The invention relates to telescopic sites for use in connection with firearms.
Present telescopic sites used on rifles and other firearms, generally comprise a cross-hair reticule positioned within the scope for referencing the hunter's vision with respect to a target. A hunter "sights in" or "zeros" the scope by firing bullets in a trial-by-error method and repetitively adjusts the reticule in the scope until the center of the cross-hair of the reticule aligns with the impact position of the bullet on the target. Such a method of zeroing a rifle requires considerable time and the costly firing of bullets.
U.S. Pat. No. 2,094,623 issued to F. E. Stokey in 1937, discloses a telescopic sight in which two reticules are utilized to enable the rifle to be zeroed in with a single shot. The Stokey device, however, was quite expensive and complicated. Also, because the hunter always views two reticules within his field of vision through the scope, it was quite possible that the hunter would inadvertently sight on the incorrect reticule. Also, the reticule which was sited in on target, could be off center from the field of vision through the scope causing further confusion and irritation to the hunter. Further, the hunter was shooting upside down with the Stokey scope, because the image through the scope was inverted due to the use of an objective and an ocular lens.
While the Stokey scope of 1937 suggested one-shot sighting, the inherent disadvantages, expense and complication of the system voided its general use. Since 1937, the prior art has suggested the use of an inverting tube to erect the object to be viewed through the scope by the hunter thus, eliminating upside down shooting by the hunter. The use of an inverting tube further establishes the center of the cross-hair wires at the center of the scope's field of vision despite adjustment of the cross-hair reticule relative to the image being viewed. The advent of the inverting tube was thus well received by the hunter.
When using an inverting tube within a scope, the reticule is positioned at the eye piece end of the tube. This is because the positioning of the reticule at the object end of the inverting tube causes the magnification of the cross-hairs of the reticule at high powers of the scope, particularly where the scope has zoom capabilities for changing the object's magnification. Such magnification of the cross-hair wires is annoying to the hunter, blocking portions of his view. Thus, present day scope manufacturers utilize an inverting tube with cross hair wires positioned at the eye piece end of the inverting tube.
Besides the problem of multiple firings to sight-in present day scopes, a problem of parallax exists when using the scope to shoot at close range. Parallax is caused by the cross-hair wires lying outside the image plane in conjunction with the hunter varying the position of his eye relative to the scope as he does not each time look across the cross-hairs at the same visual angle.
Further problems with such conventional scopes include the addition of devices which serve to approximate range and determine the "hold over" or aiming point in view of the range of the target. Particularly, the rifleman must judge the distance of the object and then compensate for the drop of the bullet in view of the weight and velocity of the bullet. Thus, the hunter must point the scope above the target in order for the bullet to drop onto the target.
Such range finding devices include, for example, the use of a transparent reticule disc at one end of an inverter tube, which bears separate circles for denoting range, see for example U.S. Pat. No. 3,392,450 issued to G. L. Herter et al. on July 16, 1968. Other such range defining devices include stadia lines which take the form of two parallely disposed horizontal lines positioned across the field of view of the hunter for his use to determine whether the object fits within the lines in order to guage distance of a targeted object.
All of these range finding devices add clutter to the hunter's field of vision and are particularly annoying when the hunter is shooting at close range and thus not using the range finding devices.